Scanning probe microscopy (SPM) devices, such as atomic force microscopy (AFM) devices as described above are for example applied in the semiconductor industry for scanning of semiconductor topologies on a surface. Other uses of this technology are found in biomedical industry, nanotechnology, and scientific applications. In particular, AFM may be used for critical defect metrology (CD-metrology), particle scanning, stress- and roughness measurements. AFM microscopy allows visualization of surfaces at very high accuracy, enabling visualization of surface elements at sub-nanometer resolution.
The very high resolution and accuracy of this technology however comes at the cost of performance in terms of throughput. Atomic force microscopy is performed by tracing of a sample surface in a scanning motion using a probe tip touching or tapping (i.e. repeatedly touching) the surface, while accurately measuring disposition of the probe tip in a direction transverse to the sample surface (z-direction) using for example a high precision optical sensing system, e.g. using beam deflection or an interferometer. Scanning is performed by vibrating the tip in the z-direction, while performing the scanning motion across the surface to be mapped. To accurately map a given section of a sample surface, e.g. a structure on a wafer surface, the probe tip requires to be scanned such that every fraction of the section with sub-nanometer dimensions is touched or tapped by the probe tip at least once. As will be appreciated, this process may be rather slow.
Further development of the SPM technology has provided AFM systems comprising a probe head upon which a plurality of probes are mounted side by side. Each probe comprises a cantilever and a probe tip, and each probe tips position in z-direction is measureable independently. This allows for scanning of a plurality of ‘scanning lanes’ at one pass of the scanning head, and as will be appreciated, the speed at which a single section may be scanned is multiplied by the number of probe tips present on the head.
Even though the above has lead to an improvement in throughput, the scanning of multiple sites on a sample surface still takes a considerable amount of time. For this and other reasons, application of this technique in industrial environments, for example for the testing of wafers in semiconductor industry, is far from ideal.